Age and sex-specific differences of the intrafemoral and intratibial morphology using the Citak classification in patients undergoing total knee arthroplasty.

Abstract

Purpose: Unlike established knee phenotype classifications, the recently introduced Citak classifications describe the intrafemoral and intratibial knee morphology. The aim of this study was to evaluate the distribution of Citak types A, B and C of the distal femur and proximal tibia in a large cohort and to examine the influence of age, body mass index (BMI) and knee phenotypes.

Methods: A total of 8739 patients undergoing primary total knee arthroplasty (TKA) were included in this study. The coronal plane alignment of the knee (CPAK) and functional knee phenotypes were assessed on standardised preoperative long leg radiographs (LLR) using a validated artificial intelligence (AI) software. The Citak classification was measured manually, and BMI, sex and age were compared between the different Citak types.

Results: The most common morphotypes were Citak type B of the distal femur (men: 1362 (46.5%); women 3042 (52.4%)) and Citak type C of the proximal tibia (men: 2605 (88.9%); women 5406 (93.0%)). Women with Citak type C of the distal femur (mean age 71.45a; p < 0.001) and proximal tibia (mean age 69a; p < 0.001) were significantly older, while no age differences were observed among men. Citak type A of the distal femur and proximal tibia had an overall higher BMI in both men and women.

Conclusion: The Citak types of the distal femur and the proximal tibia are age, sex and BMI dependent in patients undergoing primary TKA. Recognising these morphological variations might improve preoperative planning and implant selection in TKA, potentially improving patient outcomes. The Citak classification is useful to further characterise various knee morphotypes.

Level of evidence: Level III.